Computer networks allow multiple computers, peripherals and other information storage, retrieval or processing devices to share data. Each device attached to a network is typically referred to as a node on the network, or a node that is part of the network. Local Area Networks (“LANs”) have historically consisted of nodes interconnected by physical telecommunications media (e.g., coaxial cable, twisted pair wire, or fiber optics). Recently wireless LANs, the nodes of which are not connected by means of a physical medium, have started to appear in the market. These wireless LANs communicate by means of infra-red (IR), radio or other signals. One of the benefits of using wireless LANs is that cabling is not required. This is a particularly useful feature for mobile nodes such as laptop and notebook computers, PDAs (personal digital assistants), and the like. If equipped with an appropriate wireless adapter, the mobile nodes can move around within a predefined coverage area and remain connected to the network.
In order for the nodes of a particular network to be able to communicate with each other, some sort of common addressing scheme must be implemented. In a traditional wired network, one very common method of communicating between nodes is to utilize Internet Protocol (“IP”) addressing. When a node initially joins a network operating with the Internet Protocol, it is assigned an IP address consisting of at least two portions: a network address and a destination address. IP addresses are typically fixed and remain with the node irrespective of whether the node relocates to another network. In a traditional wired network, the fixed nature of IP addresses is not problematic because nodes are stationary and consequently do not migrate to networks outside of their original home network. Recently, wireless nodes have been added to traditionally hard-wired networks. Like all devices adhering to the Internet Protocol, mobile devices are accorded IP addresses having a network portion and a device portion. The network portion identifies the mobile device's “home network” while the device portion distinguishes the mobile device from other members of its home network. The routing of data packets through the Internet is generally exclusively based upon the network portion of the destination IP address. Specifically, Internet routers extract the destination network address from a given data packet and then forward that packet to the appropriate network. Once the packet reaches the appropriate network, the network server examines the device portion of the IP address and forwards the packet to the appropriate device.
When a mobile device is located in its home network, data packets addressed to a particular mobile device are simply sent to such device upon being received at the home network's access point. This process is transparent to the user so long as the mobile unit is located within range of its home network. However, when the mobile device travels outside of its home network data packets cannot easily be forwarded thereto and are often “dropped”, which results in loss of data.
Several methods have been proposed to allow mobile devices to continue IP-based communication even when moving between networks having different IP addresses. One such technique requires that the mobile unit report changes in its address to the access point or network manager in its home network. A router located in its home network stores each new IP address for the mobile unit and forwards any incoming packets to the mobile device's new IP address. An alternate approach involves establishing a pseudo presence, also called a “spoofed address,” at the mobile's home network location. However, when mobile devices frequently move between networks having different IP addresses, these address-mapping and forwarding techniques can result in packets being forwarded to multiple locations, which may cause confusion and loss of data.